KR102138444B1 - Dab receiver and frame synchronization method therefor - Google Patents

Abstract

The DAB receiver includes a fast Fourier transformer that receives a signal and performs fast Fourier transform; And a frame synchronous position detector for finding a reference position for frame synchronization by using the output of the fast Fourier converter, wherein the frame synchronous position detector receives the output of the fast Fourier converter and at least a part of the PRS signal. , A second correlation calculator for calculating a correlation between the output of the fast Fourier transformer and the signals of the at least some PRSs; And a second peak detector that detects a position of a maximum value of the correlation calculated by the second correlation calculator.

Description

DAV receiver and its frame synchronization method{DAB RECEIVER AND FRAME SYNCHRONIZATION METHOD THEREFOR}

The present invention relates to a DAB receiver and a frame synchronization method thereof, and more particularly, a DAB receiver capable of searching for frame synchronization of a DAB receiver using a PRS (Phase Reference Symbol) included in a frame of a DAB signal and a frame synchronization method thereof It is about.

1 shows a frame structure diagram of a Digital Audio Broadcasting (DAB) standard.

As can be seen from FIG. 1, one frame of the DAB standard takes 96 ms and consists of a total of 76 OFDM symbols.

In addition, one frame includes a null signal, a phase reference symbol (PRS) signal, a fast information channel (FIC) signal, and a main service channel (MSC) signal.

Among them, a null signal and a PRS signal are divided into synchronization symbols, and a FIC signal and an MSC signal are divided into data symbols.

Since the null signal indicates the beginning of the frame with no signal at all, frame synchronization can be found by searching for the null signal.

The existing frame synchronization method using a null signal basically tracks the position of the null signal using a power difference between the data symbol and the null signal. The null signal at the beginning of every frame has very little power since there is almost no data except for some Tansitter Identification Information (TII) data. This null signal was able to know the start of the frame by using the power difference between data symbols with relatively large power.

The null signal method is simple since it is intuitively performed on the time axis of the fast Fourier transformer. However, since the null signal is a method that does not have power, it is vulnerable to noise and adjacent signals. That is, since the power difference between the data symbol and the null signal is used, the probability of an error in power calculation is very high due to external factors such as noise, adjacent and co-channel. In addition, when a large number of TII signals exist due to many SFNs (Single Frequency Network) and multipath fading, there is a possibility that the null signals exist in large power. This causes a fatal problem in frame synchronization using a null signal.

2 is an exemplary diagram of the power of a null signal and a null counter signal in a noise-free environment. In addition, FIG. 3 is an exemplary diagram of power of a null signal and a null counter signal in an environment in which noise is present.

The method of finding the start of the frame by finding the position of the null signal that comes at the beginning of the frame is as follows. Since the symbol before the null signal has normal power, the power of the previous symbol and the current symbol are compared with each other, and if the power difference is large, it is determined as a null signal. 2 shows a method of finding a null signal of a normal DAB signal. You can check the power difference from the previous symbol, and if there is a power difference over a certain range, increase the counter. If the counter value is above a certain value, it is judged as a null signal.

As can be seen from FIG. 3, it can be seen that the frame synchronization method using a null signal is greatly affected by noise. It can be confirmed that the power in the null signal exists than the normal DAB signal, and the counter value also increases and decreases repeatedly.

As described above, when power is present in a null signal such as a noise environment, a multi-pass environment, an adjacent channel environment, and a complex environment, the probability of an error in frame synchronization for finding a position of the null signal increases.

The present invention is an invention aimed at solving the technical problems as described above, without using the power of the null signal, and using the PRS signal to find the position of the PRS signal and use it to search for frame synchronization DAB The aim is to provide a receiver and its frame synchronization method.

The DAB receiver of the present invention comprises: a fast Fourier transformer that receives a signal and performs a fast Fourier transform; And a frame sync position detector for finding a reference position for frame sync using the output of the fast Fourier transformer.

In addition, one frame of the signal received by the DAB receiver includes a null signal, a phase reference symbol (PRS) signal, a fast information channel (FIC) signal, and a main service channel (MSC) signal. It is characterized by.

Specifically, the frame synchronization position detector receives the output of the fast Fourier transformer and the signals of at least a part of the PRS, and calculates a correlation between the output of the fast Fourier transformer and the signals of the at least some PRS signals. Degree calculator; And a second peak detector that detects a position of a maximum value of the correlation calculated by the second correlation calculator.

In addition, the at least part of the PRS signal is characterized in that the portion of the entire PRS signal excluding the first portion contacting the null signal and the second portion contacting the FIC signal. In addition, the position of the maximum value of the correlation calculated by the second correlation calculator is a reference position for frame synchronization.

Preferably, the DAB receiver of the present invention comprises: a symbol synchronization position detector for finding a reference position for symbol synchronization of the received first signal; A buffer buffering the first signal using the reference position of the symbol synchronization output from the symbol synchronization position detector; And a parallelizer converting and outputting the serial signal output from the buffer into a parallel signal. In addition, the output of the parallelizer is input to the fast Fourier converter.

Specifically, the symbol synchronization position detector calculates a first correlation that receives the first signal and the second signal and performs a convolution operation to calculate a third signal that is a correlation between the first signal and the second signal. group; A delayer delaying the third signal to output the second signal; And a first peak detector that detects a position of a maximum value of the correlation calculated by the first correlation calculator. In addition, the position of the maximum value of the output of the first correlation calculator detected by the first peak detector becomes a reference position for symbol synchronization.

A frame synchronization method in a DAB receiver according to the present invention, comprising: a fast Fourier transform step of receiving a signal and performing a fast Fourier transform; And a frame synchronization position detection step of finding a reference position for frame synchronization using the output of the fast Fourier transform step. In addition, one frame of the signal received by the DAB receiver includes a null signal, a phase reference symbol (PRS) signal, a fast information channel (FIC) signal, and a main service channel (MSC) signal. It is characterized by.

Specifically, in the frame synchronization position detection step, receiving the output of the fast Fourier transform step and at least a portion of the PRS signal, and calculating the correlation between the output of the fast Fourier transform step and the signal of the at least some PRS Calculating a second correlation; And a second peak detection step of detecting a position of a maximum value of the correlation calculated by the second correlation calculation step.

In addition, the at least a portion of the PRS signal is characterized in that a portion of the entire PRS signal excluding the first portion contacting the null signal and the second portion contacting the FIC signal. In addition, the position of the maximum value of the correlation calculated by the second correlation calculation step becomes a reference position for frame synchronization.

Preferably, the frame synchronization method of the present invention comprises: a symbol synchronization position detection step of finding a reference position for symbol synchronization of the received first signal; A buffering step of buffering the first signal using a reference position of the symbol synchronization output from the symbol synchronization position detection step; And a parallelization step of converting and outputting the serial signal output from the buffering step into a parallel signal.

Specifically, in the symbol synchronization position detection step, a first correlation diagram that receives a convolution operation by receiving the first signal and the second signal and calculates a third signal that is a correlation between the first signal and the second signal Detection step; A delay step of delaying the third signal to output the second signal; And a first peak detection step of detecting a position of a maximum value of the correlation calculated by the first correlation detection step. In addition, the position of the maximum value of the output of the first correlation detection step detected by the first peak detection step becomes a reference position for symbol synchronization.

According to the DAB receiver and the frame synchronization method of the present invention, without using the power of the null signal, it is possible to find the location of the PRS signal using the PRS signal and use it to search for frame synchronization.

1 is a frame structure diagram of a Digital Audio Broadcasting (DAB) standard.
2 is an exemplary diagram of the power of a null signal and a null counter signal in a noise-free environment.
3 is an exemplary diagram of power of a null signal and a null counter signal in an environment in which noise is present.
4 is a block diagram of a DAB receiver according to an embodiment of the present invention.
5 is an explanatory diagram for finding a reference position for symbol synchronization by the symbol synchronization position detector of the present invention.
6 is an explanatory diagram for finding a reference position for symbol synchronization by the frame synchronization position detector of the present invention.
7 is a simulation result for frame synchronization according to the DAB receiver of the present invention.
8 is a simulation result for frame synchronization according to the DAB receiver of the present invention in a noisy environment.

Hereinafter, the DAB receiver and its frame synchronization method according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

It goes without saying that the following examples of the present invention are only intended to embody the present invention and do not limit or limit the scope of the present invention. From the detailed description and examples of the present invention, what can be easily inferred by experts in the technical field to which the present invention pertains is interpreted as belonging to the scope of the present invention.

First, FIG. 4 shows a configuration diagram of a DAB receiver 100 according to a preferred embodiment of the present invention.

As can be seen from FIG. 4, the DAB receiver 100 according to the preferred embodiment of the present invention includes a symbol synchronization position detector 10, a buffer 20, a parallelizer 30, a fast Fourier transformer 40, and It comprises a frame synchronization position detector 50.

The first signal received by the DAB receiver 100 of the present invention is an OFDM-type DAB signal and has a frame structure as shown in FIG. 1.

One frame of the first signal, that is, one frame of the signal received by the DAB receiver 100 includes a null signal, a phase reference symbol (PRS) signal, a fast information channel (FIC) signal, and an MSC. It consists of (Main Service Channel) signal.

The symbol synchronization position detector 10 serves to find a reference position for symbol synchronization of the received first signal.

Specifically, the symbol synchronization position detector 10 includes a first correlation calculator 11, a delay 12, and a first peak detector 13.

The first correlation calculator 11 serves to receive a first signal and a second signal and perform a convolution operation to calculate a third signal that is a correlation between the first signal and the second signal.

The delayer 12 serves to delay the third signal and output the second signal.

In addition, the first peak detector 13 serves to detect the position of the maximum value of the third signal, which is the correlation calculated by the first correlation calculator 11. In addition, the position of the maximum value of the output of the first correlation calculator 11 detected by the first peak detector 13 becomes a reference position for symbol synchronization.

5 is an explanatory diagram for finding a reference position for symbol synchronization by the symbol synchronization position detector 10 of the present invention.

Frame synchronization using the PRS signal is performed at a stage after the fast Fourier transformer 40, so the starting point of the 2048-point fast Fourier transform (DAB reference) must be known. For this, the symbol synchronization must first be obtained, unlike the conventional one. To this end, in the present invention, a guard interval (OFDM) signal of OFDM is used.

That is, the guard interval signal is a signal obtained by copying a portion of one OFDM symbol data. For example, the first part of OFDM symbol data can be copied and used as a guard interval signal.

Accordingly, the position of the maximum value of the output of the first correlation calculator 11 detected by the first peak detector 13 on the OFDM symbol data has elapsed by a guard interval period from the starting position of the OFDM symbol data. Become a branch.

The buffer 20 serves to buffer the first signal using the reference position of the symbol synchronization output from the symbol synchronization position detector 10. That is, the buffer 20 buffers the reference position of the symbol synchronization output from the symbol synchronization position detector 10 by the starting point of the fast Fourier transformer 40, and thus performs the fast Fourier transformation of the fast Fourier transformer 40. It serves to adjust the starting point.

The parallelizer 30 converts and outputs a serial signal output from the buffer 20 into a parallel signal.

In addition, the frame synchronization position detector 50 serves to find a reference position for frame synchronization using the output of the fast Fourier transformer 40. To this end, the frame synchronization position detector 50 is preferably configured to include a second correlation calculator 51 and a second peak detector 52.

The second correlation calculator 51 receives the output of the fast Fourier transformer 40 and the signals of at least a portion of the PRS, and calculates the correlation of the output of the fast Fourier transformer 40 and the signals of at least a portion of the PRS Plays a role. In addition, the second peak detector 52 serves to detect the position of the maximum value of the correlation calculated by the second correlation calculator 51.

At least a part of the PRS signal used in the second correlation calculator 51 is characterized in that the entire PRS signal is a part excluding the first part contacting the null signal and the second part contacting the FIC signal. Specifically, it is preferable that at least a part of the PRS signal used by the second correlation calculator 51 is a signal corresponding to 1/2 of all PRS signals.

The position of the maximum value of the correlation calculated by the second correlation calculator 51 becomes a reference position for frame synchronization. That is, in the blocks after the fast Fourier transformer 40 of the DAB receiver 100, the frame of the output of the fast Fourier transformer 40 using the position information of the maximum value detected by the second peak detector 52 Processing is performed in synchronization.

6 is an explanatory diagram for finding a reference position for symbol synchronization by the frame synchronization position detector 50 of the present invention.

After buffering in the buffer 20 using the reference position of OFDM symbol synchronization, the fast Fourier transformer 40 performs fast Fourier transform of all symbols, and the second correlation calculator 51 performs PRS for all symbols. The PRS signal is found by correlating with the signal. In addition, the symbol signal after the fast Fourier transform is obtained by obtaining a correlation with the 1/2 PRS pattern, where 1/2 PRS uses the center portion of the symbol.

That is, in the DAB receiver 100 of the present invention, the basic concept is that a portion of a known PRS signal is used to find a correlation with a DAB symbol to obtain the position of the PRS signal.

The PRS signal is a signal of the Known pattern defined in the DAB standard, and the correlation is calculated using only 1/2 PRS pattern, which is a part of the PRS signal, to minimize the computation amount. Since this is done at the rear end of the fast Fourier transformer 40, it is necessary to know the synchronization of the symbols in advance. In addition, another reason to use only the 1/2 PRS pattern is that the complexity of the system can be reduced to half, and the front and rear parts of the symbol may be destroyed by multipath fading, so the front and rear parts are not used and the center Find the correlation of the frame by finding the correlation using only half based on.

After obtaining the symbol synchronization using the guard interval of the OFDM symbol in advance, a fast Fourier transform is performed, and the correlation between the fast Fourier transform result and the PRS signal pattern can be seen that the section having the highest correlation is the PRS signal. Since the PRS signal is located after the null signal, synchronization of the frame can be naturally found.

As shown in FIG. 6, it can be seen that the PRS exhibits high correlation. That is, as a result of calculating the correlation by the second correlation calculator 51, at the end of the 1/2 PRS signal, the maximum value of the correlation appears, and this position is the second peak as a reference position for frame synchronization. The detector 52 will detect it.

7 shows simulation results for frame synchronization according to the DAB receiver 100 of the present invention.

In FIG. 7, blue indicates a PRS signal and the rest indicates a data symbol. It can be seen that the blue color of PRS has high correlation. Through this, the location of the PRS can be known and frame synchronization can be found.

8 shows simulation results for frame synchronization according to the DAB receiver 100 of the present invention in a noisy environment.

8, it can be seen that according to the present invention, frame synchronization can be found using PRS even at a low SNR.

Hereinafter, a frame synchronization method in the DAB receiver 100 according to an exemplary embodiment of the present invention will be described. Since the frame synchronization method of the present invention uses the above-described DAB receiver 100, it is needless to say that it includes all the features of the DAB receiver 100 even if not otherwise described.

A frame synchronization method in the DAB receiver 100 according to an exemplary embodiment of the present invention includes: a symbol synchronization position detection step of finding a reference position for symbol synchronization of an input first signal; A buffering step of buffering the first signal using the reference position of the symbol synchronization output from the symbol synchronization position detection step; And a parallelization step of converting and outputting the serial signal output from the buffering step into a parallel signal.

In addition, one frame of the first signal, that is, one frame of the signal received by the DAB receiver 100, a null signal, a phase reference symbol (PRS) signal, and a fast information channel (FIC) signal And a MSC (Main Service Channel) signal.

Specifically, the symbol synchronization position detection step includes: a first correlation detection step of receiving a first signal and a second signal and performing a convolution operation to calculate a third signal that is a correlation between the first signal and the second signal; A delay step of delaying the third signal to output a second signal; And a first peak detection step of detecting a position of a maximum value of the correlation calculated by the first correlation detection step.

In addition, the position of the maximum value of the output of the first correlation detected by the first peak detection step is the reference position for symbol synchronization.

In addition, the frame synchronization method in the DAB receiver 100 according to an exemplary embodiment of the present invention includes: a fast Fourier transform step of receiving an output of a parallelization step and performing a fast Fourier transform; And a frame synchronization position detection step of finding a reference position for frame synchronization using the output of the fast Fourier transform step.

Specifically, in the frame synchronization position detection step, a second correlation diagram for receiving the output of the fast Fourier transform step and the signals of at least a portion of the PRS, and calculating the correlation between the output of the fast Fourier transform step and the signals of at least a portion of the PRS Calculation step; And a second peak detection step of detecting a position of a maximum value of the correlation calculated by the second correlation calculation step.

In addition, it is preferable that at least a part of the PRS signal is a part of the entire PRS signal excluding the first part contacting the null signal and the second part contacting the FIC signal. In addition, the position of the maximum value of the correlation calculated by the second correlation calculation step becomes a reference position for frame synchronization.

In the above-described DAB receiver 100 of the present invention and its frame synchronization method, a PRS signal is used rather than a conventional null signal method. That is, conventionally, the power difference between the null signal and the data signal is used on the time axis before the fast Fourier transform, whereas in the present invention, the PRS position can be found using a known pattern of the PRS signal on the frequency axis after the fast Fourier transform. Through this, in the present invention, the frame synchronization can be obtained by finding the PRS signal located after the null signal.

100: DAB receiver
10: symbol synchronization position detector
20: buffer
30: parallelizer
40: fast Fourier converter
50: frame sync position detector
11: first correlation calculator
12: delay
13: first peak detector
51: 2nd correlation calculator
52: second peak detector

Claims (12)

In the DAB receiver,
A symbol synchronization position detector for finding a reference position for symbol synchronization of the received first signal using a guard interval signal;
A buffer buffering the first signal using the reference position of the symbol synchronization output from the symbol synchronization position detector;
A parallelizer converting and outputting a serial signal output from the buffer into a parallel signal;
A fast Fourier transformer that receives the output signal of the parallelizer and performs a fast Fourier transform; And
It includes; a frame synchronization position detector for finding a reference position for frame synchronization using the output of the fast Fourier transformer;
One frame of the signal received by the DAB receiver,
A DAB receiver comprising a null signal, a phase reference symbol (PRS) signal, a fast information channel (FIC) signal, and a main service channel (MSC) signal. According to claim 1,
The frame synchronization position detector,
A second correlation calculator that receives the output of the fast Fourier transformer and the signals of at least a portion of the PRS, and calculates a correlation between the output of the fast Fourier transformer and the signals of the at least some PRS; And
And a second peak detector for detecting a position of a maximum value of the correlation calculated by the second correlation calculator. According to claim 2,
The at least some of the PRS signal,
DAB receiver, characterized in that the portion of the entire PRS signal except for the first portion contacting the null signal and the second portion contacting the FIC signal. According to claim 2,
DAB receiver, characterized in that the position of the maximum value of the correlation calculated by the second correlation calculator is a reference position for frame synchronization. delete According to claim 1,
The symbol synchronization position detector,
A first correlation calculator for receiving the first signal and the second signal and performing a convolution operation to calculate a third signal that is a correlation between the first signal and the second signal;
A delayer delaying the third signal to output the second signal; And
It includes; a first peak detector for detecting the position of the maximum value of the correlation calculated by the first correlation calculator;
DAB receiver, characterized in that the position of the maximum value of the output of the first correlation calculator detected by the first peak detector is a reference position for symbol synchronization. In the frame synchronization method in the DAB receiver,
A symbol synchronization position detection step of finding a reference position for symbol synchronization of the received first signal using a guard interval signal;
A buffering step of buffering the first signal using a reference position of the symbol synchronization output from the symbol synchronization position detection step; And
A parallelization step of converting and outputting a serial signal output from the buffering step into a parallel signal;
A fast Fourier transform step of receiving a signal output from the parallelization step and performing a fast Fourier transform; And
Including the frame synchronization position detection step of finding a reference position for frame synchronization using the output of the fast Fourier transform step;
One frame of the signal received by the DAB receiver,
A frame synchronization method comprising a null signal, a phase reference symbol (PRS) signal, a fast information channel (FIC) signal, and a main service channel (MSC) signal. The method of claim 7,
The frame synchronization position detection step,
A second correlation calculation step of receiving the output of the fast Fourier transform step and the signals of at least a part of the PRS, and calculating a correlation between the output of the fast Fourier transform step and the signals of the at least some PRS; And
And a second peak detection step of detecting a position of a maximum value of the correlation calculated by the second correlation calculation step. The method of claim 8,
The at least some of the PRS signal,
A frame synchronization method characterized in that it is a part of the entire PRS signal except for the first part contacting the null signal and the second part contacting the FIC signal. The method of claim 8,
A frame synchronization method, characterized in that the position of the maximum value of the correlation calculated by the second correlation calculation step becomes a reference position for frame synchronization. delete The method of claim 7,
The symbol synchronization position detection step,
A first correlation detection step of receiving the first signal and the second signal and performing a convolution operation to calculate a third signal that is a correlation between the first signal and the second signal;
A delay step of delaying the third signal to output the second signal; And
The first peak detection step of detecting the position of the maximum value of the correlation calculated by the first correlation detection step; includes,
A frame synchronization method, characterized in that the position of the maximum value of the output of the first correlation detection step detected by the first peak detection step becomes a reference position for symbol synchronization.

Images